I have found on two separate occasions that when calling United Reservations and searching for flights, they don't immediately see the 10,000 mile one ways. For example, I've booked three segments between ORD and CMH which is less than 700 miles each way. On the phone, the agent only offers me 12,500 mile awards. You need to politely ask that they look for 10,000 mile flights under "Award Options"

I discovered this after insisting that the agent talk to her supervisor because she was convinced the 10,000 mile flights were either an online special or I was mistaken.

As a remind though, the 10,000 mile award replaces the 12,500 mile award when there is Saver Award availability and the segment is <700 miles.